1. Field of the Invention
This invention relates to the construction of combustion chambers and, in particular, to a construction of longitudinally arranged channels or similar tubular elements forming closed corrosion-resistant channels for transporting a corrosive cooling medium such as in a combustion chamber wall, or the like.
2. Description of the Prior Art
Regenerative cooling in liquid-propellant rocket combustors or combustion chambers is a widely applied method for improving the capability of combustor walls to withstand thermal stress. It also affords greater dynamic strength against the forces arising from the internal pressure of the combustion chamber due to the temperature differences that occur in operation. The regenerative cooling method commonly feeds one or more of the propellant components through channels in the combustion chamber wall for cooling purposes before they are injected into the combustion chamber.
In one known design for regenerative cooling, the wall to be cooled has capillary tubes of varying cross sections. These capillary tubes are dimensioned and arranged symmetrically about the longitudinal axis of the combustion chamber in such a manner that they touch each other laterally along their entire length. In this form of design, an electroplated layer making contact with the radial outer surface lines of the tubes provides the pressure-tight bonding of the tubes. However, undesirable deformations of the tubes when exposed to operational conditions tend to cause irreparable leaks.
Yet another known method for regenerative cooling in rocket combustors incorporates a radially extending inner row and a radially extending outer row of cooling ducts encircling the interior surface of the thrust nozzle of the neck portion, with the ducts extending longitudinally into the convergent and divergent portions. This arrangement, involving two separate rows of ducts, calls for a complex method of construction which in turn lends itself to a greater possibility of structural failure.
Thus, in the past, to overcome the physical and thermal stress associated with regenerative-type fluid-cooled combustion chambers, the number of coolant channels were increased or the thickness of the portions of the combustor walls between the hot-side surface of the combustor and the coolant channels were minimized. Also, combining those two approaches and improving the method of electrodepositing protective coatings on the channel wall surfaces have been tried without complete satisfaction.